Control system with variable length messages and plural decoder levels



Oct. 29, 1968 R. G. GABRIELSON 3,408,626 CONTROL SYSTEM WITH VARIABLELENGTH MESSAGES AND PLURAL DECODER LEVELS Filed July 16, 1964 5Sheets-Sheet 1 CENTRAL REMOTES STATION 03 IQUALITATIVE COMMAND I6 (PUMPSTART) -03003OHI6I6HH (INTERPOSE RELAY CLOSES FOR PUMP START)-OOHUUUUUUO3HH QUALITATIVE STATUS (SELF INITIATES QUALI- TATIVE STATUSDUE TO (GARBLED MESSAGE) CHANGE OF STATE OF PUMP START MONITOR RELAY)IINITIATE QUALITATIVE STATUS MESSAGE REPLY) OOHUUUUUUO3HH (DISPLAYSQUALITATIVE STATUS MESSAGE INFORMATION) r STORES SET POINT NUMBER ANDCONVERTS TO ANALOG SIGNAL INVENTOR Re/dar 6. Gabrie/son ATTYS.

Oct. 29, 1968 R. G. GABRIELSON 3,408,626

CONTROL SYSTEM WITH VARIABLE LENGTH MESSAGES AND PLURAL DECODER LEVELSFiled July 16, 1964 5 Sheets-Sheet 2 FRAME I FRAME 2 HOLE HOLE REPEAT12/52/5) 2/5 2/5 2/5] 2/5 I NONE I NONE I ADDRESS LABEL ADDRESS LABELNEUTER NEUTER COMMUNICATION 22 COMMUNICATION CIRCUIT BASIC RECEIVERBASIC TRANSMIT CHANNEL CHANNEL MONITORED OPERATING M EQUIPMENT M M I7 ISMEAR OUTPUT l4 l6 I I TO INTERPOSE I' 'rlag-m m 15m l5 I8 20 v I .J

ANALOG SIGNAL IN VEN TOR. ReidcIr G. Gabrie/son Fig. 3 BY MEM Oct. 29,1968 R. G. GABRIELSON 3,408,626

CONTROL SYSTEM WITH VARIABLE LENGTH MESSAGES AND PLURAL DECODER LEVELSFiled July 16, 1964 I 5 Sheets-Sheet 5 COMMUNICATION CIRCUIT QUALITATIVECOMMAND CONTROLS QUALITATIVE DISPLAY 8| QUANTITATIVE DRIVES QUANTITATIVECOMMAND C ONTROLS LOGGING COMPLEX 42 DATA LoGGER Fig.4

SQUELCH MARK SPACE IN (RxI) (RxO) 53 55, 56 I INvERTER SCHMIDT BLoCKING"0"B TS I 52 AMP. TRIGGER osc. V OUT 57 INvERTER SCHMIDT BLOCKING g AAMF? TRIGGER osc. INvERTER i 54 I B C G I"BITS I: g g' OUT BI 59 58 II60 63 62 AMP AND "BIT" TIMER BIT TIMER RELAY IO BIT 5 BIT DECODE CEMESSAGE END CONTACTS INVENTOR. Reidar G. Gabrie/son F/g.5

ATTYIB.

1968 R. G. GABRIELSON CONTROL SYSTEM WITH VARIABLE LENGTH MESSAG ANDPLURAL DECODER LEVELS Filed July 16, 1964 5 Sheets-Sheet 5 GATE OPENDECODE SECURITY LOGIC INVALID MESSAGE GATE OPEN 20 UNITARY OUTPUTSINVENTOR. Reidar G. Gabrie/son BY MESSAGE ig.

INCORRECT MESSAGE ArTYs.

United States Patent 3 408,626 CONTROL SYSTEM WITH VARIABLE LENGTHMESAGES AND PLURAL DECODER LEVELS Reidar G. Gabrielson, Scottsdale,Ariz., assignor to M0- torola, Inc., Franklin Park, 11]., a corporationof Illinois Filed July 16, 1964, Ser. No. 383,202 5 Claims. (Cl.340-163) ABSTRACT OF THE DISCLOSURE Supervisory control system having acentral station and a plurality of remote stations munication line.length to a level for each message length thereto by a first or messageare made for checking length decoder.

made selectively responsive length decoder. Provisions in each decodinglevel and fords an unusual degree of system flexibility.

dominant considerations in the designing of width is a practicallimitation Aside from bandwidth and on message length. system speedconsiderations,

able-length messages.

Another object of the invention is and decoding equipment of messages bytypes and the use of part of the message structure to identify differenttypes of messages.

The de- 3,408,626 Patented Oct. 29, I968 coding equipment includes afirst level which recognizes the message type information and routes themessage to another decoding level which decodes the functionalinformation in messages of that type. Thus,

dling of messages.

In the accompanying drawings:

FIG. 1 is a word picture showing schematically how one embodiment of theinvention handles different types of messages;

FIG. 2 illustrates pictorially the structure of three different types ofmessages included in the system operation depicted in FIG. 1;

basic receiver channel block diagram for a second level decoder unitshown in FIG. 4.

sage type label, and in the the label is zero in this embodiment.

The manner in which the quency. Each information digit of the message isalso five bits long,

mote station is then 030030H 1616HH.

The message is accepted by the third remote station called for by themessage, which in this case is the of a relay to start a pump. Remotestation 03 then sends two digits are the label which identifies themessage type.

For qualitative messages the label may be zero, and there are two zeroessince the label is repeated. There are no digits identifying theaddressee in remote-to-central messages. After the decode hole (H) thereis a series of unitary digits (U) followed by the senders address 03.Information represented by the unitary digits are used to bring statusdisplays at the central station up to date.

To further illustrate the types of messages handled by the system, itwill be assumed that the qualitative status message from station 03becomes so garbled by noise on the communication channel thatit isrejected by the central station. The latter station then sends a smearmessage to all remote stations of the system to cause any station whichhas transmitted within a fixed time immediately preceding the smearcommand to repeat the message.

Since the smear message goes to all stations, the digits for the smearfunction (90 in this system) are at the beginning of the first frame inplace of the address word. The zero following the smear digits 90 merelyfills out the message structure-it signifies only that the message willbe decoded by a first level decoder as will be explained further. In thesecond frame the digits 900 are repeated for message security purposes,and this second message frame is followed by two holes signifying theend of the message.

Although all three remote stations receive the smear message, onlystation 03 responds to it since it is the only station which transmitteda message during the preceding reference time interval. The thirdstation responds to the smear message by repeating the qualitativestatus message as shown in FIG. 1. This message is received at thecentral station and causes the central station to update the qualitativestatus display for the third remote station.

In the last line of FIG. 1, the central station is shown sending aquantitative command to the second remote station 02. The particularcommand shown in FIG. 1 is a quantitative command 0627 for adjusting theset point of a controller associated with the remote station 02. Thecode for this command is 021021H06270627HH, and its message structure isshown in FIG. 2 at the bottom. The first frame is the station address 02and the message type 1. The second frame is simply a repeat of the firstframe and is followed by a hole. The third frame contains the set pointinformation 0627, and again the fourth frame is a repeat of the thirdframe. In this embodiment, the set point information is encoded inbinary coded decimal form (BCD). The end of the message is denoted bytwo holes as before. The second remote station 02 accepts thequantitative command and the other two remote stations reject it asshown in FIG. 1. The second remote station performs the set pointadjustment function as called for by the quantitative command.

From the foregoing description of FIGS. 1 and 2, it will be apparentthat the system is designed to handle messages of different types anddifferent lengths. The variable message length capability makes itpossible to tailor individual messages to the information contained inthem and the functions to be performed by them as previously mentioned.The messages may be encoded using different codes as indicated by FIG.2. Reference is made to application Ser. No. 299,727 filed Aug. 5,

1963, by the present inventor for further examples of the use of unitarycode, binary coded decimal and the 2/5 code referred to above.

FIG. 3 is a block diagram of a typical remote station which is designedto handle messages of various lengths. The circuits illustrated in FIG.3 may be used for any of the remote stations of a supervisory controlsystem in accordance with the invention. The remote station has acommunication circuit 11 which receives incoming messages and supplieselectrical signals representing the message bits to the basic receiverchannel 12. One of the functions of the receiver channel is to convertthe electrical signals to current pulses and shape them to be compatiblewith the decoding circuitry. The current pulses are then supplied to thedecoding levels 13, 14 and 15. Since these decoder levels are designedto decode messages of a given number of digits, the designation used isDE followed by a number identifying the number of digits. The firstlevel handles three digits and therefore is designated DE-3, the secondlevel handles two digits and so is designated DE-Z, and the third levelfor handling four digits is designated DE-4.

The decoder levels are preconditioned such that the first level 13 isgated open prior to the beginning of the message and therefore acceptsthe message pulses, whereas the second and third levels 14 and 15 aregated closed and do not initially accept the message pulses. Assumingthat a qualitative command message has been received by the remotestation shown in FIG. 3, the message will be processed by the decoderlevels as follows. The first two words (030030) will be accepted andstored by the first decoder level 13. The first decoder level includesmessage security circuitry which checks the first two message frames todetermine if the message is correct. Such message security circuits willbe described more fully later, but in general if the message containsthe correct number of bits and if each two corresponding bits of the twomessage frames are identical, the first decoder level 13 will be enabledto decode the message. On the other hand, if the message contains otherthan the correct number of bits, or if any two corresponding hits arenot the same, the first decoder level will reject the message.

Decoding is initiated by a decode command generated by circuitry withinthe basic receiver channel 12 responsive to the hole at the end of thesecond message frame. Assuming that the first two message frames arecorrect, the decode command causes the first level decoder 13 to decodethe first two message frames and gate the second level decoder 14 open.At the same time, the first decoder level 13 is gated closed.

The second decoder level 14 then accepts the third and fourth messageframes in the qualitative command message. These frames are checked forcorrectness by message security circuitry in the same general manner asjust described in connection with the first decoder level. If the thirdand fourth message frames are correct, they will be decoded by thedecoder level 14 in response to a command signal generated by the basicreceiver channel 12 during the time of the first hole at the end of themessage. The second decoder level 14, upon decoding the message,

- supplies outputs to a further decoding stage 16 associated with thesecond level decoder. The latter decoder stage, identified CO-ZA,supplies stretched output signals which are routed to interpose relaysto initiate the function called for by the qualitative command. In thecase being described, the qualitative command 16 causes the remotestation to actuate interpose relays which start a pump, but there aremany different types of qualtative functions which can be performed bythe remote station.

The manner in which the remote station of FIG. 3 decodes a smear messagewill now be described to point out the differences in operation ascompared to decoding of the qualitative status command. As has beendescribed, the smear message has only two frames, and it is decodedcompletely by the first level decoder 13. As before, the first leveldecoder checks the message to determine if it is correct, and if it iscorrect, decodes the message responsive to the first hole at the end ofthe message. The first decoder level recognizes this message as a smearcommand and supplies a smear output to the basic transmit channel 21which causes the preceding message to be repeated. The two holes at theend of the smear message merely ensure that the first level decoder 13is reconditioned to accept the next message.

the case of a quantitative command message, the

tative and logging commands.

In the previous description of FIG. 1, a sequence of messages Wasdescribed station then repeats its last message which identified assquelch, mark, and space. The squelch input is processed by an inverteramplifier 51 which resteep leading and trailing edges.

Outputs are supplied from the trigger circuits 54 and 55 to an or gate59. So long as pulses are being supplied the blocking oscillators 56, 57and 58 to another or gate 61 which in turn controls two timers 62 and63. The five bit timer 62 responds to a vide a decode a message endcommand.

The leading edge of a mark pulse (receive one) actuates trigger circuit54 which in turn fires the blocking oscillator to produce a binary oneoutput pulse. The trailing edge pulse which is the of that mark pulsecauses the trigger circuit 54 to switch back to its original state andsupply an output to the 57 causing it to produce an output phase Aclocking pulse. If the next its leading edge changes the state of thetrigger circuit 55 which in turn fires the blocking oscillator 56 toproduce a zero output pulse. At the same time, an output is suppliedfrom the trigger circuit 55 to the blocking oscillator 57 to reconditionthat oscillator and make it responsive to the next output from the othertrigger circuit 54.

The one, zero and clock pulses are supplied from the receiver channel toinput terminals 71, 72 and 73 respectively of a first decoder level suchas that shown in FIG. 6.

blocking oscillator pulse is a space pulse (receive zero),

The decoder of FIG. 6 is the DE-3A module used in the remote station ofFIG. 3. The one and zero pulses pass through the decoder gate 74 and arefed serially into three five-bit shift registers 76, 77 and 78. Sincethe DE-3A decoder is designed to handle three digits of a message, thetotal capacity of the three shift registers must be fifteen bits becausethere are five bits per digit.

The first three digits of an incoming message (the first message frame)will load the shift registers 76, 77 and 78 to capacity. As the secondmessage frame arrives, it will shift out serially the first messageframe and supply it via line 79 to the message security logic circuitry81. This input to the message security logic may be considered as thefirst message frame delayed. The second message frame is supplieddirectly to the message security logic via inputs 82 and 83. Incomingclock pulses are supplied from terminal 80 to the-logic circuitry 81 andto the shift register 76 in order to provide the necessary timing.

The logic circuitry 81 includes a counter which counts the .bitsarriving at inputs 82 and 83. For every five bits registered by thecounter, it produces an output called an advance pulse which steps ascanner 86 one step. At the end of the first message frame, the scannerhas advanced three steps and is midway through its scanning cycle. Atthis time, the scanner produces a mid-count output which goes to thelogic circuitry 81 via line 87. The mid-count signal causes the logiccircuitry to start comparing the second message frame with the firstmessage frame.

As long as each two corresponding bits of the first and second messageframes are identical, the counter of the logic circuitry will continueto advance. By the time the second message frame has been receivedcompletely, the three shift registers 76, 77 and 78 are loaded tocapacity with the second message frame. Meanwhile, the scanner 86 hasadvanced to the end of its scanning cycle, and at this time produces acorrect count output on line 88.

A short time after the correct count output, the decode command signalarrives at terminal 89. The decode signal turns off the gate 74 andreads out the message security logic. If the logic circuitry has countedthirty hits, it produces the correct message pulse which goes via line91 to the scanner 86 and to shift registers 77 and 78. The correctmessage pulse resets the scanner and reads out the information stored inthe shift registers.

The shift registers 77 and 78 supply parallel outputs of which has tenoutput lines. decode the first two digits of the meswould ordinarily bethe address of the receiving station. The other shift register 76suppliesits outputs to a decoder 94 which decodes the message labeldigit. Decoder 94 also has ten output lines, and these outputs areconnected to the gate open controls of the decoder gates of otherdecoding levels included in the station. Thus, the message may be any often different types and as many as ten different decoding levels may becontrolled by the DE-3A first level decoder shown in FIG. 6.

One of the outputs from decoder 92 and one output from decoder 93 aresupplied to a further decoder 96 for decoding system housekeepingcommands. These com- The latter sage which mands are sent to allstations of the system, and an example is the smear command described inconnection with FIG. 1. In the particular embodiment being described,the decimal digits 90, 91, 92 and 93 are reserved for systemhousekeeping commands, and the decimal digit is assigned to smearcommands. Y

Another output from each of the two decoders 92 and 93 is fed via aprogram plug 97 to a decoder 98' which activates a module 143 forsupplying reading current to the shift register 76. Thus, the correctmessage output from the logic circ 'try 81 reads out shift registers77and 78, and the decoded address from the latter shift registers causesthe other shift register 76 to be read out via the reading module 99.

If the counter of the logic circuitry 81 registers a count of somethingother than 30 after the end of the message, it produces an incorrectmessage output on line 101'. When the decode signal arrives at terminal89, it will read out the message security logic circuitry and an invalidmessage output will appear on line 102. The decode signal also closesthe gate 74 and'reset's the scanner 86 if the message was incorrect.Since there will be no correct message output on line 91, the shiftregisters 76, 77 and 78 will not be read out, and the message will notbe decoded. I

The other decoding levels of the system are similar to the DE-SA decodershown in FIG. 6, but will be designed to handle a different number ofdigits. FIG. 7 shows a simplified block diagram for a DE-1 decoder suchas the first level decoder 34 of FIG. 4. As previously mentioned, thisdecoder handles only one digit, and so only one five bit shift register111 is required. For the same reason, the scanner 112 has only twosteps, and the counter of the message security logic circuitry 113 willcount up to ten if the message is correct. The decoder gate 114 and thedecoding module 115 corresponds to modules 74 and 92 in FIG. 6. Thesequence of operation is also the same as has been described inconnection with FIG. 6.

FIG. 7 is a functional block diagram for a DE-4 de coder such as tion ofFIG. 4. This decoding level has the same functional blocks as the DE1decoder of FIG. 7, but is designed to decode four digits. Therefore, thescanner 116 has eight steps and the shift register 117 has a twenty bitcapacity. The counter of the message security 118 will register twentycounts for a correct message. A decoder gate 119 and an output decoder120 are again provided as previously described.

The shift registers of the equipment which has been described may beconstructed with true and complement magnetic cores in the mannerdescribed and claimed in application Ser. No. 229,852, filed on Oct. 11,1962, by L. R. Smith and assigned to the present assignee. The decodermodules which receive outputs from the shift registers may beimplemented with toroidal cores in the manner described and claimed inapplication Ser. No. 299,727, filed on Aug. 5, 1963, and assigned to thepresent assignee. The latter application and also application Ser. No.299,- 859, filed on Aug. 5, 1963, by R. G. Gabrielson and L. R. Smithdescribe and claim the housekeeping aspects of the system and alsodisclose specific circuits which may be used to implement the systemdescribed herein. Accordingly, the disclosure of circuits in thoseapplications is incorporated herein by reference.

The invention provides a variable message length capability for digitalsupervisory control systems which makes more efficient use of availablebandwidth than a fixed length message structure. By identifyingmessagesby type,

I and through the use of level-by-level decoding as described optimizethe length and structure of each message for its function andinformation content. An important advantage is the ease with which agiven system can be expanded after installation without requiringextensive modification of the original equipment.

herein, it is possible to a first station including encoding means forencoding message, said encoding means being adapted to en- 4. A digitalsupervisory control system including in code information in a firstportion of the message for combination, identifying different types ofmessages some of which a first station including encoding means forencoding have different lengths and to encode further informa messagescomprising a series of binary coded bits tion in succeeding portions ofthe mes age, with uncoded gaps between different portions of the asecond station including a receiving channel for rem s ag Whi h p rti nshave diff rent lengths, Said ceiving messages from said first station, afirst decoder encoding means being adapted to encode informalevelcoupled to said receiving chamiel having means tion in a first portionof the message for identifying to decode only a first portion of themessage including 5 di ferent types of messages and to encode furtherinmessage type information therein to provide a control formation insucceeding portions of the message, signal, a plurality of additionaldecoder levels coupled and a second station including a receivingchannel for to said first decoder level for decoding portions of areceiving messages from Said first Station, a first message followingsaid first portion thereof, said adcoder level coupled to said receivingchannel havditional decoder levels being selectively rendered reingmeans to decode only a first portion of the messponsive to a message bysaid control signal from sage including message type informationtherein, and said first decoder level, with the selection of a parhavingfurther means to check the length of said ticular one of said additionaldecoder levels dependfirst message portion and operative to reject anying on the message type information in the first pormessage having afirst portion of an incorrect length, tion thereof. a plurality ofadditional decoder levels coupled to 2. A digital supervisory controlsystem comprising: said first decoder level for decoding portions of a acentral station including encoding means for encoding message followingsaid first portion thereof, said messages comprising a series of binarycoded bits additional decoder levels being selectively rendered withuncoded gaps between diiferent portions of the responsive to a messageby said control signal, and message, said encoding means being adaptedto eneach of said additional decoder levels having means codeinformation in a first portion of the message to check the length of themessage portion decoded for identifying different types of messages andto thereby and to reject any message in which that encode furtherinformation in succeeding portions of message portion is of an incorrectlength. the message, 5 A supervisory control system having a centralstaa remote station including a receiving channel for retion and aplurality of remote stations oined by a comceiving messages from saidcentral station, a first demon communication system with each remotestation havcoder level coupled to said receiving channel having ing aunique address, the improvement including in coma plurality of outputportions and having means to bination, decode only a first portion ofthe message including means in the central station for transmitting tothe message type information therein to provide a control communicationsystem a plurality of signals includsignal at a particular one of saidoutput portions ing signals indicating an address of a selected remotecorresponding to the message type, a plurality of adstation, a messagelabel and a message having a ditional decoder levels coupledrespectively to said length corresponding with said label, outputportions of said first decoder level for decodmeans in each remotestation for receiving said transing portions of a message following saidfirst portion mitted signals including basic receiver channel meansthereof, said additional decoder levels being selectiveresponsive tosaid address signals indicating the ad- 1y rendered responsive to amessage by a 6 mm] dress of the respective remote station to decode saidsignal from said first decoder level so that said fi st label indicatingsignals and supply control signals indecoder level routes the message toa selected one of length corresponding with said label, said additionaldecoder levels in accordance With t a plurality of decoder levels ineach remote station each message type information. capable of decoding adiiferent length message and 3. A digital supervisory control systemcomprising: respectively responsive to said control signals to deacentral station including encoding means for encodcode said messageindicating signals received from ing messages comprising a series ofbinary coded the respective said remote station receiving means bitsWith uncoded p between ditfefent Portions of and error detection meansin each level for detecte s said encoding means e adapted to ing saidlength correspondence of said message lndlencode station addressinformation and message type catmg s gnals h Said label slgnals and saldinformation in a first Portion the message and t0 coder levels beingoperative to supply indicia of said encode further information insucceeding portions of message indicating signals only when said errordethe message, tection means detects such correspondence. a plurality ofremote stations, each including a receiving channel for receivingmessages from said central References Cited station, a first decoderlevel coupled to said receiv- UNITED STATES PATENTS ing channel having aplurality of output portions and having means to decode only the firstportion of the I message including the station address and message typeinformation therein to provide a control signal 3,110,013 11/1963Bt'eese 4 -1 3 at a particular one of said output portions correspond-3,223,970 12/1965 Abbott 6t 31 340-147 ing to the message typeinformation, a plurality of I 1 additional decoder levels coupledrespectively to said JOHN CALDWELL Examl'leroutput portions of saidfirst decoder level for decod- H. PITTS, Assistant Examiner.

ing portions of a message following said first portion 3,175,191 4/1965Cohn et 31. 2,989,730 6/1961 Brosh.

